Method of making sandblast stencils



L. D. RICHARDSON METHOD OF MAKING SANDBLAST STENCILS April 20, 1965 2 Sheets-Sheet 1 Filed Aug. 31, 1961 April 20, 1965 D. RICHARDSON 3,179,729

METHOD OF MAKING SANDBLAST STENCILS Filed Aug. 31, 1961 2 Sheets-Sheet 2 United States Patent 3,179,729 METHOD 01F MAKING SANDBLAST STENQZHLS Lucius D. Richardson, 207 N. Rockford Ave,

Rockford, Di. Filed Aug. 31, 1961, Ser. No. 135,313 6 Claims. (Cl. 264-216) This invention relates to 'an improved method of producing a resilient stencil for sandblast carving and the like. 7

In sandblast carving, it has heretofore been the practice for the artist to first prepare the design on paper; manually transfer the design onto a resilient sheet of material such as rubber, and then manually cut out the design from thesheet of resilient material to form a resilient stencil for use in sandblast carving. Considerable time is required to transfer the design onto the resilient sheet and to cut out the design from the resilient sheet to form the stencil and, as a consequence, the production' of sandblast carvings has been relatively expensive. Moreover, such procedure is not well suited for reproduction of intricate designs because of the problem of cutting out fine detail from the sheet of resilient material.

An important object of this invention is to provide an improved method for producing resilient stencils for sandblast carving which avoids the difiiculties heretofore encountered in manually transferring the design onto the sheet of resilient material and manually cutting the design from-the sheets, and which improved method enables resilient sandblast stencils to be rapidly and economically produced.

Another object'of this invention is to provide a method of producing resilient stencils for sandblast carving which employs photoengraving techniques to produce a resilient stencil while enabling the use of resilient materials for the stencil which are themselves not etchable in the photoengraving processes.

A more particular object of this invention is to provide a method of producing sandblast stencils in which the design is first etched completely through an etchable plate by photoengraving techniques to form openings in the plate corresponding to the design, and a layer of resilient sandblast-resistant material is thereafter applied to the areas remaining on the face of the plate after the openings have been etched therein, to thereby form a resilient stencil for use in subsequent sandblast carving operations.

These, together with various ancillary objects and advantages of this invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description when taken in connection with the accompanying drawings wherein:

FIG. 1 is a diagrammatic view illustrating the produc tion of the original design;

FIGS. 6 and 7 are fragmentary diagrammatic views illustrating the steps of etching the plate completely through to form openings in the plate corresponding to the original design;

FIG. 8 is a diagrammatic view illustrating the application of a layer of resilient material to the areas remaining 3,179,329 Patented Apr. 20, 1965 on the plate after the design has been etched therethrough;

FIG. 9 is a diagrammatic view illustrating the step of cleaning the openings in the resilient stencils;

FIG. 10 is a diagrammatic view illustrating the separation of the resilient stencil from the engraved plate;

FIG. 11 is a diagrammatic view illustrating the application of an adhesive to the resilient stencil for use in applying the same to the object to be carved;

FIG. 12 is a diagrammatic view illustrating the use of the resilient stencil in sandblastcarving;

FIG. 13 is a fragmentary View illustrating an arrangement for connecting separated portions of a stencil to enabl reuse of the stencil;

FIG. 14 is a fragmentary view illustrating the completed sandblast carving;

FIGS. 15 and 16 are diagrammatic perspective views illustrating difierent ways of using the sandblast stencils; and

FIG. 17 is an enlarged fragmentary sectional view through the stencil, taken on the'plane 1717 of FIG. 12.

The method of the present invention employs photoengraving processes asan intermediate step in the production of a resilient stencil for sandblast carving, and the design to be reproduced in the stencil may accordingly be produced in any manner that will result in an opaque image on a transparent background for printing on a photo-engraving plate. As diagrammatically illustrated in FIGS. 1-3, the original design is drawn out by an artist to produce a black image designated 10 on a white background 11. The black on white design is then photographed as by a camera diagrammatically illustrated in FIG. 2 anddesignated 13 to produce a negative designated 11a in which the design appears as transparent areas 10a. The desired opaque image on a transparent background is then produced by printing the transparent negative on a sheet of film designated 11b, as by a printing apparatus designatedlS, to produce an opaque image 10b corresponding to the original design. As is apparent, the design can be enlarged or reduced during the steps of photographing and printing diagrammatically illustrated in FIGS. .2 and 3. Alternatively, the original design could be produced as a white design on a black background in which event the initial step of photographing the design shown in FIG. 2 would produce the desired opaque design on a transparent background. If desired, the original artists sketch could be in the form of a black design on a transparent background, in which event the steps of producing the photo-negative and the photo-positive shownin FIGS. 2 and 3 could both be omitted.

The opaque design lid on a transparent background 11b is then printed on a photoengraving plate. The plate is formed of an etchable material, for example zinc, magnesium, copper, photo-engravers plastic. etc. which can be etched by acid, and is made sufi'icien-tly thick to be form sustaining. The plate is coated on one side with a light sensitive coating designated 21 which may be of any well known composition such as are commonly used in photoengraving plates, and which sensitive coating forms an insoluble etch-resistant layer on the face of the plate 22, when the coating is exposed to light. The opaque design lla shields the light sensitive coating 21 on the plate from the rays of the printing apparatus 17 so that the portion of the coating underlying the design remains soluble while the remainder of the light sensitive coating is exposed to the light through the transparent background 11b and becomes an insoluble etch-resistant cover. The plate 22 is then washed or developed in a developing apparatus diagrammatically illustrated at 23 in FIG. to remove those areas of thelight sensitive coating which were not exposed to light during the printing and the plate thereafter hardened in a suitable hardening bath. The design designated 2i) then appears in the removed areas of the light sensitive coating 21, while the remaining areas of the light sensitive coating form an acid resistant negative of the original art work. The back of the etchable plate 22 is covered with a suitable acid resistant protective coating designated 25, of any well known composition used for this purpose in photoengraving, for example inks or enamels, and the plate is subjected to an etching bath diagrammatically indicated at 27. The plate is etched in the uncovered areas of the design formed in the etch resistant coating 21. It is necessary in accordance with the present invention to etch the design completely through the plate 22. For a relatively thin plate such as are suitable for use in small size designs, it is possible to completely etch the plates through from one side, suitable precautions being taken in accordance with good engraving practice to prevent excessive undercutting of the design as the plate is etched therethrough. However, for relatively thick plates, it is preferable to etch the design from both sides of the plate to minimize the problems usually encountered in photoengraving due to undercutting and the like. As shown in FIG. 6, the design is only etched half-way through the plate in the initial etching bath to form an intaglio image designated 3!) corresponding to the original design. The plate is then removed from the bath, washed and dried and a protective coating may be applied to the etched side of the plate to protect the same during subsequent operations, if desired. The protective covering at the other or rear side is removed and a photosensitive coating designated 21' in FIG. 7 is applied to the rear side of the plate. The opaque design 11a is then printed on the light sensitive coating 21' on the rear side of the plate, in the same manner as shown in FIG. 4, and means such as the locating openings 33 and 34 in the plate 22 and the transparent positive llllb may be used to assure registry of the designs printed on opposite sides of the plate. The unexposed areas of the light sensitive coating 21' which were shielded by the opaque design lllla are then washed or developed out in the manner illustrated in FIG. 5 to form uncovered areas designated 20' at the rear side of the plate corresponding to the design. The plate is reimmersed in the etching bath 27, as shown in FIG. 7, to etch the plate completely through from the rear side thereof and form openings 39 in the plate corresponding to the original design.

The open grid-like plate is then used in the formation of a resilient sandblast-resistant stencil. The resilient stencil is formed of a resilient material, for example rub ber, neoprene or the like, which will stand the heat and abrasive action during sandblasting. The resilient material is applied in a liquid or finely divided state to the face areas remaining on the plate after the design openings have been etched therethrough, and the material may be applied by spraying, rolling, dipping or electrical deposition to form a layer designated 40 of a suitable thickness for sandblast carving. The resilient layer 40 applied to the plate 22 will have openings 4% therein corresponding to the opening 39 in the plate to provide a resilient stencil having the desired design. The thickness of the layer will vary dependent upon the material used in forming the resilient stencil and also vary with different materials to be carved. For example, the pressures and duration of the sandblasting operation for carving in soft materials such as wood is substantially less than that encountered in carving relatively hard materials such as stone, so that relatively thin resilient stencils can be used for the soft materials whereas relatively thicker resilient stencilsare generally required for hard materials. The resilient layer designated 40 can be applied in successive coatings as by spray apparatus 41 to build up the layer thickness. It has been found that when the resilient material is sprayed onto the plate 22, the force of the spray blows through the openings and tends to maintain the openings clear and prevent bridging of the openings. In order to further clean the openings, it is advantageous to direct a jet of air or a light sandblast stream through the openings in the plate 22 from the rear side thereof, as by an apparatus 35 diagrammatically shown in FIG. 9, and preferably prior to hardening of the resilient layer 40, to clean the stencil. When the resilient stencil forming material is sprayed onto the grid-like plate 22, the edges of the resulting stencil around the etched openings in the plate taper or fiare outwardly in a direction away from the plate, as shown in FIG. 17. This taper or flare in the design openings in the stencil is particularly advantageous in the sandblast carving of small intricate designs since it facilitates the entrance and rebound of the sandblast stream into and out of the small stencil openings.

The resilient stencil 40 may be used for sandblast carving while attached to the plate 22 in which case the plate can function as a backing plate for supporting the stencil. It is preferable, however, to remove the resilient stencil at) from the plate 22 as shown in FIG. 10 to enable reuse of the plate 22 for producing additional stencils. In addition, removal of the resilient stencil from the backing plate also minimizes the overall thickness of the stencil to enable more accurate sandblast carving and to also enable the stencil to be applied to non-planar surfaces. In order to facilitate removal of the resilient stencil from the plate 22, the plate is preferably coated with a parting agent prior to application of the resilient material thereto. The parting agent may be of the type which dissolves upon immersing the plate in a suitable solution such as water or, alternatively, may be of a material such as paraffin which softens at a low temperature below the decomposition temperature of the resilient coating material to enable separation of the resilient stencil from the plate 22.

The resilient stencil is thereafter applied to the article to be carved. As diagrammatically shown in FIG. 11, the back of the stencil is coated with a suitable adhesive, as by a coating apparatus 45, and the stencil 40 then affixed to the article 46 to be carved. In the particular stencil illustrated, tie bars 47 were used to hold certain parts of the stencil together during the stencil forming operation. These tie bars are preferably removed as shown in FIG. 12 as by cutting prior to the sandblast operation, to enable completion of the sandblast carving in a single operation. In order to preserve the stencil for reuse, the separate portions of the stencil are conveniently joined together by a removable piece of tape 48 or the like as shown in FIG. 13, which tape is applied to the stencil after the sandblast operation and prior to removal of the stencil from the workpiece to prevent loss of centers. When the sandblast stream is directed against the face of the stencil as by a sandblast apparatus diagrammatically shown at 50 in FIG. 12, the resilient stencil 40 protects the face of the workpiece 46 except in the open areas 4% corresponding to the design. The sandblast stream thus produces an intaglio image 40' in the workpiece corresponding to the original design.

FIGS. 15 and 16 illustrate an alternative use of the stencil. As diagrammatically illustrated, the resilient stencil is used while it remains attached to the plate 22 so that the plate forms a rigid backing to aid in handling the stencil. The tie bars 4'7 in the stencil are retained during the step of sandblast carving to hold the separate parts of the stencil together so that the intaglio image 55' cut into the workpiece has uncut segments 47 in the areas which underlie the tie bars on the stencil. These uncut segments can be subsequently removed, if desired, as by a fine sandblast carving nozzle 56 or other carving tool, as illustrated in FIG. 16.

From the foregoing, it is thought that the method of the present invention will be readily understood. As is apparent, the method enables the production of resilient stencils without requiring manual transfer of the designs onto the stencil sheet or manual cutting ofthe stencils. Moreover, the method is adapted for use on very intricate designs. The stencils may be formed of any suitable resilient material which can withstand the heat and abrasion of sandblast carving and which is adapted for application on the etched plate by spraying, dipping, rollers or electrodeposition. While the stencil is herein shown applied to stone workpieces, it is apparent that the stencil can be used in sandblast carving of other materials such as wood, plastics, etc.

I claim:

1. The method of making resilient stencils for sandblast carving and the like comprising, producing an etch resistant coating on a plate of etchable material in a design, etching completely through said plate in the areas not covered by the coating in said design to form openings in said plate corresponding to said design, and thereafter applying a resilient sandblast-resistant material only on the face areas remaining on said plate after the openings have been etched through said plate to form a resilient sandblast-resistant layer having openings therein corresponding to the openings in the plate.

2. The method of making resilient stencils for sandblast carving and the like comprising, producing an etch resistant coating on a plate of etchable material in a design, etching completely through said plate in the areas not covered by the coating in said design to form openings in said plate corresponding to said design, applying a resilient sandblast resistant material only on the face areas remaining on said plate after the openings have been etched through the plate toform a resilient sandblast-resistant layer having openings therein correspondstate only on the face areas remaining on the plate after the openings have been etched through the plate and causing a high velocity stream of fluid to pass through the openings in the plate while the resilient material is in a liquid state to clean the openings and thereby form a resilient sandblast-resistant layer having openings corresponding to the openings in the plate.

4. The method of making resilient stencils for sandblast carving and the like comprising, printing a positive of the design on a lightsensitive coating on an etchable plate, washing the unexposed areas of the light sensitive coating from the plate, etching completely through the plate in the areas not covered by the coating to form openings in the plate corresponding to said design, applying a coating of parting agent to the plate, applying a resilient sandblast-resistant material in a liquid state on top of the coating of parting agent only on the face areas remaining on the plate after the openings have been etched through the plate and causing a high velocity stream of fluid to pass through theopenings in the plate while the liquid material is in a liquid state to cleanthe openings and thereby form a resilient sandblast-resistant layer having openings corresponding to the openings in the plate, and thereafter removing the resilient layer from the plate after the material has set for use as a sandblast stencil.

5. The method of making resilient stencils for sandblast carving comprising, printing a positive of the design on a light sensitive coating on one side of an etchable plate, washing the unexposed areas of the light sen sitive coating from said one side of the plate, etching part way through the plate from said one side in the the areas not covered by the coating, printing the same design on a a light sensitive coating on the other side of the plate in registery with the design on said one side, etching from said other side of the plate in the areas not covered by the light sensitive coating completely through the plate to the etched areas on said one side to form openings in the plate corresponding to said design, and applying a resilient sandblast-resistant material to at least one side of said plate only to the face areas remaining after the openings have been etched through the plate to form a resilient layer of sandblast-resistant material having openings therein corresponding to the openings in the plate.

6. The method of making resilient stencils for sandblast carving and the like comprising, producing an etch resistant coating on opposite sides of a plate of etchable material in a design with the designs on opposite sides of the plate in registry with each other, etching completely through the plate from relatively opposite sides in the areas not covered by the coating in said design to form openings in the plate corresponding to said design, and spraying a layer of resilient sandblast-resistant material to at least one side of the plate only on the face areas remaining after the openings have been etched through the plate to form a resilient layer of sandblastresistant material having openings therein corresponding to the openings in the plate.

References Cited by the Examiner UNITED STATES PATENTS 1,900,960 3/33 Takeda 156-3 2,695,351 11/54 Beck 156-3 XR 2,845,379 7/58 Bey 156-289 XR 2,967,766 1/61 Wetmore et a1. 156-3 XR 3,117,403 1/64 Jack et al 156-154 3,138,503 6/64 Taraud 156-3 ALEXANDER WYMAN, Primary Examiner.

EARL M. BERGERT, HAROLD ANSHER,

Examiners. 

1. THE METHOD OF MAKING RESILIENT STENCILS FOR SANDBLAST CARVING AND THE LIKE COMPRISING, PRODUCING AN ETCH RESISTANT COATING ON A PLATE OF ETCHABLE MATERIAL IN A DESIGN, ETCHING COMPLETELY THROUGH SAID PLATE IN THE AREAS NOT COVERED BY THE COATING IN SAID DESIGN TO FORM OPENINGS IN SAID PLATE CORRESPONDING TO SAID DESIGN, AND THEREAFTER APPLYING A RESILIENT SANDBLAST-RESISTANT MATERIAL ONLY ON THE FACE AREAS REMAINING ON SAID PLATE AFTER THE OPENINGS HAVE BEEN ETCHED THROUGH SAID PLATE TO FORM A RESILIENT SANDBLAST-RESISTANT LAYER HAVING OPENINGS THEREIN CORRESPONDING TO THE OPENINGS IN THE PLATE. 